1. Field of the Invention
The invention relates to a facsimile apparatus having a communicating function of a nonstandard procedure and a communicating function of a standard procedure.
2. Related Background Art
In a conventional facsimile communication, when a communication is performed between exchanges by using a digital line of, for example, 16 kb/sec, there exists a private communication system such that an analog modulated signal generated from a facsimile transmitter is once demodulated at the front stage of a transmission side exchange, thereby transmitting the signal as digital information on the digital line, and the signal is again modulated at an output stage of an exchange on the partner reception side, thereby transmitting the information as analog data to a facsimile receiver.
On the other hand, there has been proposed a facsimile apparatus such that at the time of detection of an NSF signal included in an initial identification signal, when a country code of FIF of the NSF signal is specified information, it is determined that the line is connected to a private exchange system, and a communication is performed at a specified transmitting speed which has been registered in correspondence to such a discrimination result (Japanese Patent Application No. 6-256720).
In the above-mentioned apparatus, since an exchange replaces the country code of the NSF signal to a country which does not exist, a nonstandard protocol is not performed.
There is such a private exchange that by breaking the NSF signal, a shift to the nonstandard protocol is not performed. This is because when a nonstandard signal passes, a peculiar error retransmission or the like is executed by the ARQ and a communication is impossible in a digital line of 16 kb/sec.
When the NSF signal is broken, there is a problem such that since the number of flags between the NSF signal and a CSI signal is often equal to 1 or 2, the receiver side cannot correctly receive CSI/DIS signals of the NSF/CSI/DIS signals, resulting in a pre-procedure error.
It is an object of the present invention to improve a facsimile apparatus in consideration of the foregoing problems.
Another object of the invention is to provide a facsimile apparatus such that in case of performing a communication through an exchange which does not pass a nonstandard signal, a communication error due to the transmission of the nonstandard signal is avoided and a valid communication can be assured.
The other objects of the present invention will become apparent from the following detailed description with reference to the accompanying drawings.